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Surface brightness profiles and structural parameters for 53 rich stellar clusters in the Large Magellanic Cloud
Mackey, A. D.; Gilmore, G. F.
We have compiled a pseudo-snapshot data set of two-colour observations from the Hubble Space Telescope archive for a sample of 53 rich LMC clusters with ages of 106-1010 yr. We present surface brightness profiles for the entire sample, and derive structural parameters for each cluster, including core radii, and luminosity and…
A Massive X-Ray Outflow from the Quasar PDS 456
O'Brien, P. T.; Reeves, J. N.; Ward, M. J.
We report on XMM-Newton spectroscopic observations of the luminous radio-quiet quasar PDS 456. The hard X-ray spectrum of PDS 456 shows a deep absorption trough (constituting 50% of the continuum) at energies above 7 keV in the quasar rest frame, which can be attributed to a series of blueshifted K-shell absorption edges due to highly ionized iron…
Quantitative Spectroscopy of O Stars at Low Metallicity: O Dwarfs in NGC 346
Bouret, J. -C.; Hillier, D. J.; Lennon, D. J. +5 more
We present the results of a detailed analysis of the properties of dwarf O-type stars in a metal-poor environment. High-resolution, high-quality ultraviolet and optical spectra of six O-type stars in the H II region NGC 346 have been obtained from a spectroscopic survey of O stars in the SMC. Stellar parameters and chemical abundances have been de…
The INTEGRAL/IBIS scientific data analysis
Foschini, L.; David, P.; Bird, A. J. +6 more
The gamma-ray astronomical observatory INTEGRAL, succesfully launched on 17th October 2002, carries two large gamma-ray telescopes. One of them is the coded-mask imaging gamma-ray telescope onboard the INTEGRAL satellite (IBIS) which provides high-resolution (~12') sky images of 29degx29deg in the energy range from 15 keV to …
X-Ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies
McHardy, I.; Nandra, K.; Vaughan, S. +11 more
By combining complementary monitoring observations spanning long, medium, and short timescales, we have constructed power spectral densities (PSDs) of six Seyfert 1 galaxies. These PSDs span >~4 orders of magnitude in temporal frequency, sampling variations on timescales ranging from tens of minutes to over a year. In at least four cases, the P…
A Planetary Companion to γ Cephei A
Cochran, William D.; Endl, Michael; Hatzes, Artie P. +5 more
We report on the detection of a planetary companion in orbit around the primary star of the binary system γ Cephei. High-precision radial velocity measurements using four independent data sets spanning the time interval 1981-2002 reveal long-lived residual radial velocity variations superposed on the binary orbit that are coherent in phase and amp…
The Relationship Between X-Ray Radiance and Magnetic Flux
Johns-Krull, Christopher M.; Pevtsov, Alexei A.; Longcope, Dana W. +4 more
We use soft X-ray and magnetic field observations of the Sun (quiet Sun, X-ray bright points, active regions, and integrated solar disk) and active stars (dwarf and pre-main-sequence) to study the relationship between total unsigned magnetic flux, Φ, and X-ray spectral radiance, LX. We find that Φ and LX exhibit a very nearly…
The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z = 0 to z = 3
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +11 more
We present the evolution of the rest-frame optical luminosity density jrestλ, the integrated rest-frame optical color, and the stellar mass density, ρ*, for a sample of Ks band-selected galaxies in the Hubble Deep Field-South (HDF-S). We derived jrestλ in the rest-frame U, B, and V …
Reconstruction of solar irradiance variations in cycle 23: Is solar surface magnetism the cause?
Solanki, S. K.; Krivova, N. A.; Unruh, Y. C. +1 more
A model of solar irradiance variations is presented which is based on the assumption that solar surface magnetism is responsible for all total irradiance changes on time scales of days to years. A time series of daily magnetograms and empirical models of the thermal structure of magnetic features (sunspots, faculae) are combined to reconstruct tot…
Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
Ajhar, Edward A.; Rieke, Marcia J.; Tonry, John L. +5 more
To empirically calibrate the IR surface brightness fluctuation (SBF) distance scale and probe the properties of unresolved stellar populations, we measured fluctuations in 65 galaxies using NICMOS on the Hubble Space Telescope. The early-type galaxies in this sample include elliptical and S0 galaxies and spiral bulges in a variety of environments.…